Photos, The Hypogeum in Malta, left and Tara, in Ireland.

Archaeologists have discovered Europe's oldest civilisation, a network of dozens of temples, 2,000 years older than Stonehenge and the Pyramids.

More than 150 gigantic monuments have been located beneath the fields and cities of modern-day Germany, Austria and Slovakia. They were built 7,000 years ago, between 4800BC and 4600BC.

Their discovery, revealed today by The Independent, will revolutionise the study of prehistoric Europe, where an appetite for monumental architecture was thought to have developed later than in Mesopotamia and Egypt.

In all, more than 150 temples have been identified. Constructed of earth and wood, they had ramparts and palisades that stretched for up to half a mile. They were built by a religious people who lived in communal longhouses up to 50 metres long, grouped around substantial villages.

Evidence suggests their economy was based on cattle, sheep, goat and pig farming.

Their civilisation seems to have died out after about 200 years and the recent archaeological discoveries are so new that the temple building culture does not even have a name yet.

Excavations have been taking place over the past few years - and have triggered a re-evaluation of similar, though hitherto mostly undated, complexes identified from aerial photographs throughout central Europe.

Archaeologists are now beginning to suspect that hundreds of these very early monumental religious centres, each up to 150 metres across, were constructed across a 400-mile swath of land in what is now Austria, the Czech Republic, Slovakia, and eastern Germany.

The most complex excavated so far - located inside the city of Dresden - consisted of an apparently sacred internal space surrounded by two palisades, three earthen banks and four ditches.

The monuments seem to be a phenomenon associated exclusively with a period of consolidation and growth that followed the initial establishment of farming cultures in the centre of the continent.

It is possible that the newly revealed early Neolithic monument phenomenon was the consequence of an increase in the size of - and competition between - emerging Neolithic tribal or pan-tribal groups, arguably Europe's earliest mini-states.

After a relatively brief period - perhaps just one or two hundred years - either the need or the socio-political ability to build them disappeared, and monuments of this scale were not built again until the Middle Bronze Age, 3,000 years later. Why this monumental culture collapsed is a mystery.

The archaeological investigation into these vast Stone Age temples over the past three years has also revealed several other mysteries. First, each complex was only used for a few generations - perhaps 100 years maximum. Second, the central sacred area was nearly always the same size, about a third of a hectare.

Third, each circular enclosure ditch - irrespective of diameter - involved the removal of the same volume of earth. In other words, the builders reduced the depth and/or width of each ditch in inverse proportion to its diameter, so as to always keep volume (and thus time spent) constant.

Archaeologists are speculating that this may have been in order to allow each earthwork to be dug by a set number of special status workers in a set number of days - perhaps to satisfy the ritual requirements of some sort of religious calendar.

The multiple bank, ditch and palisade systems "protecting" the inner space seem not to have been built for defensive purposes - and were instead probably designed to prevent ordinary tribespeople from seeing the sacred and presumably secret rituals which were performed in the "inner sanctum".

The investigation so far suggests that each religious complex was ritually decommissioned at the end of its life, with the ditches, each of which had been dug successively, being deliberately filled in.

"Our excavations have revealed the degree of monumental vision and sophistication used by these early farming communities to create Europe's first truly large scale earthwork complexes," said the senior archaeologist, Harald Staeuble of the Saxony state government's heritage department, who has been directing the archaeological investigations. Scientific investigations into the recently excavated material are taking place in Dresden.

The people who built the huge circular temples were the descendants of migrants who arrived many centuries earlier from the Danube plain in what is now northern Serbia and Hungary. The temple-builders were pastoralists, controlling large herds of cattle, sheep and goats as well as pigs. They made tools of stone, bone and wood, and small ceramic statues of humans and animals. They manufactured substantial amounts of geometrically decorated pottery, and they lived in large longhouses in substantial villages.

One village complex and temple at Aythra, near Leipzig, covers an area of 25 hectares. Two hundred longhouses have been found there. The population would have been up to 300 people living in a highly organised settlement of 15 to 20 very large communal buildings.